This invention relates generally to a fluid heating system and, more particularly, to a heating system which utilizes an infrared burner module having a heat exchanger coil wrapped around a radiant burner to provide both domestic hot water and space heat.
In heating systems for homes and commercial buildings, central furnaces to heat a space all operate on the same general principle. Air for a space to be heated circulates through a closed system (such as ductwork), and is heated either as it passes through a heat exchanger in contact with a burning fuel, or as it passes in contact with a secondary fluid which has been heated by a burning fuel. Since burning the fuel results in the production of noxious combustion gases having exhaust temperatures which can exceed 500.degree. F., it is necessary to exhaust the combustion gases through a chimney or flue to the atmosphere. These systems are relatively inefficient due to the high exhaust temperatures of the flue gases, and costly due to the construction of the necessary flue or chimney.
Indirect fired furnaces, ones in which the air being heated is not contacted directly by the combustion gases generated, are generally used in both forced air systems and hydronic systems.
A forced air system consists primarily of a heat exchanger having combustion chambers arranged in relation to the flow of air to be heated such that fuel is generally introduced at the lower end of the chamber where a flame causes heat to be generated. The heat rises through a series of internal baffles before exiting through an upper end of the combustion chamber into the flue or chimney. Simultaneously, circulated space air passes around the outside of the heat exchangers to absorb heat through conduction and convection.
A hydronic system consists primarily of a firebox having a heat exchanger therein. The heat exchanger is located in a closed loop system for continuously circulating water from the heat exchanger to a remote radiator in the space to be heated. However, this system is also relatively inefficient and expensive due to the combustion gas temperatures at the outlet of the firebox and the cost of the chimney.
In supplying domestic hot water for homes and commercial buildings, potable hot water systems with ordinary glass-lined, hot water storage tanks are generally used. It is common for these systems to have an enclosed water tank in which the cold water to be heated enters. At the lowermost portion of the tank there is normally a burner whose heat is allowed to pass through the tank, thereby heating the water in the tank for use within the home or building. Again, as in the space heating systems for homes and buildings, the heat which is not transferred to the heat exchanger is exhausted at the top of the tank into a flue or chimney to the atmosphere. Thus, a domestic hot water system is also inefficient because a great portion of the heat is lost directly up the chimney to the atmosphere, both during demand/on time and standby/off time, as well as being lost through the tank jacket. In addition to the inefficiencies of these systems, the flues or chimneys are costly to construct.
Because of the rising costs of energy, the incentives to conserve energy are increasing. Consequently, there is currently considerable interest in recovering energy, such as waste heat from combustion heaters which is usually injected into the atmosphere without recovery, and eliminating energy waste by making furnaces and water heaters more efficient.
In an attempt to increase the efficiency of a heating system condensing furnaces were implemented. In condensing furnaces exhaust combustion gases are used to preheat the space air prior to this air contacting the primary heat exchanger. Thus, in this type of furnace exhaust temperatures are reduced but corrosive condensates are formed as the exhaust combustion gases are reduced below their dew point.
In an attempt to reclaim rejected heat, heat exchange coils have been installed in the flue of a furnace to transfer some of the waste heat to domestic hot water heaters, thus recovering some usually wasted heat.
However, the increase in efficiency of known heating systems has not reduced the large size of the furnace. The large furnace structure is the result of the need for large heat exchange surface areas to transfer the convection heat from the combustion products to the space air or hydronic fluid. Moreover, the recovery of waste heat has not reduced the size of a water heater but in fact has increased its size. Prior art for a central installation requires a large separate furnace to heat the space and a tank type water heater to supply potable hot water.
Another problem in space heating installations and domestic hot water tanks is the loud low frequency noise associated with these systems commonly called combustion roar. This is especially true where the furnace is connected to a duct of the heating system which tends to amplify the noise.
Still another problem in previously known combustion systems is that furnaces or water heaters normally generate gaseous combustion products which include oxides of nitrogen (NO.sub.X) which are vented to the atmosphere as flue gases. It is desirable to limit these oxides of nitrogen emissions since oxides of nitrogen are considered pollutants, and gas-fired combustion systems sold in certain geographical areas must meet strict NO.sub.X emission standards.
Thus, there is a clear need for an integral space heating/hot water gas-fired system having a modular design that will, to a large extent, overcome the problems noted in the prior art.